In addition to the previous post you might want to look at my prior post in this very thread where I went on in great detail about the comparison of the Slipstream M 1200 and the Nexus 120mm.

Here is a tiny recap:

Code:

Nexus D12SL-12 12V 22dBA 1080RPM 29CFMStarting Voltage 5.5V

Code:

Slipstream M 1200 12V 28dBA 1210RPM 46CFMStarting voltage 2.4

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So, the Slipstream 1200RPM must be used at ~7v or less (21-18dBA & 890-620RPM) in order to be quieter than the Nexus (22-19dBA & 1080-490RPM). 7 volts on the SS 1200 is approximately the same noise (21dBA) as the Nexus at 12v (22dBA), while the CFM at those speeds are 30CFM vs 29CFM. The Slipstream is quieter and blows a bit more air.

In terms of noise, the 800RPM Slipstream would seem to be better (19-<18dBA) overall. (Only the 500RPM Slipstream is quieter!) And at the same RPM/noise level the 800 matches the 1200RPM. So if you can tolerate the louder noise, then the 1200RPM can give you headroom (but at the "cost" of 28dBA!), but if you want a quiet fan no matter what, the 800RPM would seem to be better.

I notice that the SH slip stream model (1900rpm) working at 9v (1340rpm) at 26dBA is quieter than the M model (1200rpm) working at 12v (1200rpm) at 28dBA, is this likely a sample variation, or the nature of these fans? If so, maybe running SH model at 9v is a better idea if I can tolerate 26dBA. Thanks.

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The RPMs we are quoting are as tested not as specified. There are many reasons why the numbers vary. We prefer to use the SPCR numbers to keep the variables to a minimum. Though I think I see what you are getting at:

There is a 1530 RPM and 1220 RPM measured in the review but they aren't labeled as medium and low. Is that a mistake in the review or a difference between specified and measured?

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i am using a 1200 on my cpu, and it is almost always spinning at around 1250, sometimes seen it reach 1300.

i also managed to get some 800's shipped to uk, and they are also running over 800.

nothing alarming, just curious. or is it just the program giving false readings. i am using everest,

Fan speed monitoring devices are just not that accurate, and the fans themselves vary a bit in rpm/voltage -- they probably all hit 1200rpm, but at slightly different voltages -- one at 11.5, another at 12, another at 12.5. I would like to actually make RPM the reference control rather than voltage, but the challenge then is to try and get the RPM readings as accurate as possible... which, as I started this note with, is hard because the tachometers are not that accurate.

I would like to actually make RPM the reference control rather than voltage, but the challenge then is to try and get the RPM readings as accurate as possible

FelgerC's stroboscopic method is good although labour-intensive, detailed in his "User Reviews" posts. also, as u note, most fans will have as much as a +/-10% variation in top speed and still be "within spec".

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I would like to actually make RPM the reference control rather than voltage, but the challenge then is to try and get the RPM readings as accurate as possible

FelgerC's stroboscopic method is good although labour-intensive, detailed in his "User Reviews" posts.

Labor-intensive because I was using one stroboscope to measure both the sensor prop RPM and the fan under test RPM. If only the fan under test, and only one desired RPM, it actually is labor-efficient to set the stroboscope to the desired RPM and adjust the fan voltage until the strobe image is stable. That can be accomplished, start to finish, more quickly than by any other method I know of.

I'm interested in going for some SH 1900rpm Slipstreams. The reason being that I need fans with a good low noise level for idle usage as they're used in a block of four, hooked up to the same fan controller output for simplicity (I will use two per channel with slipstreams due to the power usage. I'm running a Sunbeam Rheobus and Rheobus Extreme, so I'm not too worried about current draw).
The reason for going super high is this is for my gaming system, which has a pair of noisy 4870X2s in it (that are only at all noisy under load). However, since they run very hot, and on top of that I may eventually consider fitting Accelero Extremes on them when they arrive, so air blows into the case, I need a hell of a lot of airflow, so would like the full band of potential speed.

Can I just therefore check, the SFF21F at 1600 (which is a relatively powerful fan compared to most of the ones I use) is 47CFM, and these 1900rpm slipstreams are 71? A 50% increase in CFM for 20% extra rpm?
I realise the 9-blade vs 7-blade design achieves this (though I'm aware of the extra noise), but it seemed a lot, so I wanted to check before I spend Â£40 on buying four of them.

Heh, would prefer the grille to remain intact as that's all there is that makes up most of the side to my case (HAF932). 1200rpm would possibly be enough, and indeed 700rpm would probably do me in York, but even with an Ultra-120, a 1600rpm SFF21F on it, correctly fitted with good paste, my CPU reached 105ÂºC and shut down (Main temp, not cores) the other day due to the environment. I've sinced moved back to my student house and cut the temps in half, almost literally, but needless to say, some brute force cooling might do me good for when I go back in July in the peak of summer. Since the 1200rpm fan is no cheaper, I didn't see much to be lost.

I bought the 1900 RPM model based on the review, and I can't get it to go below 1300 RPM on my Abit IP35 PRO. I've tried all the different voltage options, but it simply will not go as low as the review said.

It is now spinning at 1300 RPM with a voltage of 6V, as claimed by Abit's ÂµGuru. The fan is drawing power from AUX_FAN3.

Is this sort of thing common? At least one person in this thread has had his 1900 RPM model slow down properly, so I'm thinking WTH.

Fans like the Slipstream actually speed up exponentially with voltage. If you had 6V instead of 12V, the fan should really be below half speed. A common failing of software fan controllers is that they don't have anywhere near as much of a range as they say. A software controller I used to use claiming 6-12V actually only went from 8V-10.5V. I suspect that is what is happening here. Run the fan through a hardware fan controller and you will get a much lower speed out of it I'm sure.

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